1. Field of the Invention
The invention relates to a vehicle control apparatus and a vehicle control method.
2. Description of the Related Art
There has been developed a method that, in order to drive through a corner in a shortest possible time, sets a time of passage through the corner as an evaluation function, and computes an ideal locus by using an optimization technique.
For example, in “Numerical Analysis of Minimum-Time Cornering—The Fourth Report: Road Constraints Using Inequality Constraints on State Values—” by Takehiko Fujioka and Daisuke Emori, Transactions of Society of Automotive Engineers of Japan, Vol. 24, No. 3, July 1993, p.106-111, it is described that the Sequential Conjugate Gradient-Restoration Algorithm (SCGRA) that is used to compute an optimum locus of an artificial satellite, a space shuttle, etc., is applied to calculation of motion of a vehicle, and the time of passage through a corner is set as the evaluation function in order for the vehicle to pass through the corner in the shortest time.
Besides, Japanese Patent Application Publication No. 2008-275621 (JP-A-2008-275621) discloses a technology that determines a travel route by using an evaluation function. In the technology, using an evaluation function that represents a lower limit of the cost related to the route to a destination relative to a vertex, a value of an evaluation function based on a first graph is determined, and on the basis of the determined value of the evaluation function, a route from the departure point to the destination on a second graph is searched for.
Besides, Japanese Patent Application Publication No. 10-302199 (JP-A-10-302199) provides a disclosure related to a technology that performs an optimizing control of a lateral displacement on the basis of an evaluation function and constraint condition. The disclosure is that a steering actuator is controlled so that the lateral displacement detected by a magnetic sensor becomes equal to a targeted lateral displacement, whereby the sliding velocity of the vehicle in the lateral direction relative to the magnetic source at the position of the magnetic sensor is reduced.
However, in conjunction with the foregoing travel locus optimization technology, there is no disclosure as to the manner in which values for determining convergence, such as the equation of motion, a constraint condition, a boundary condition, etc., should be set. In the case where a travel plan of a motor vehicle or the like is to be calculated by using the optimization technique, it is difficult in the related technologies to appropriately set a condition for convergence determination while taking into account vehicle stability, computation time, etc.
That is, the calculation of a travel locus ends in the case where the evaluation function is determined as having converged. If, in a simulation, a condition for determining that the function has converged is set strict, the computation accuracy heightens but a long computation time is needed. On the other hand, if the constraint condition is set less strict, the calculation ends in an early period, but it becomes necessary to make a contrivance regarding the relaxation of the convergence condition in order to maintain vehicle stability in an actual travel.